Using mathematical induction, the numbers $$a_n \delta$$ are defined by $$a_0=1, a_{n+1}=3 n^2+n+a_n, (n \geq 0)$$. Then, $$a_n$$ is equal to

If $$49^n+16^n+k$$ is divisible by 64 for $$n \in N$$, then the least negative integral value of $$k$$ is

$$2^{3 n}-7 n-1 \text { is divisible by }$$

The total number of terms in the expansion of $$(x+y)^{60}+(x-y)^{60}$$ is